diff --git a/embed.module b/embed.module
index 2834b39..3cb178d 100644
--- a/embed.module
+++ b/embed.module
@@ -6,8 +6,10 @@ use Drupal\Core\StringTranslation\TranslatableMarkup;
 
 /**
  * Implements hook_form_FORM_ID_alter() on behalf of ckeditor.module.
+ *
+ * @todo Remove this once CKEditor4 support is dropped.
  */
-function ckeditor_form_embed_button_add_form_alter(array &$form, FormStateInterface $form_state) {
+function ckeditor_form_embed_button_add_form_alter(array &$form, FormStateInterface $form_state): void {
   $form['#validate'][] = 'ckeditor_form_embed_button_add_form_validate';
 }
 
@@ -16,8 +18,10 @@ function ckeditor_form_embed_button_add_form_alter(array &$form, FormStateInterf
  *
  * Checks to make sure that when adding a new embed button, its ID will not
  * conflict with any existing CKEditor buttons.
+ *
+ * @todo Remove this once CKEditor4 support is dropped.
  */
-function ckeditor_form_embed_button_add_form_validate(array &$form, FormStateInterface $form_state) {
+function ckeditor_form_embed_button_add_form_validate(array &$form, FormStateInterface $form_state): void {
   /** @var \Drupal\ckeditor\CKEditorPluginManager $ckeditor_plugin_manager */
   $ckeditor_plugin_manager = \Drupal::service('plugin.manager.ckeditor.plugin');
 
@@ -25,11 +29,11 @@ function ckeditor_form_embed_button_add_form_validate(array &$form, FormStateInt
   $button_ids = array_reduce($ckeditor_plugin_manager->getButtons(), function ($result, $item) {
     return array_merge($result, array_keys($item));
   }, []);
+  $button_ids = array_map('mb_strtolower', $button_ids);
 
   // Ensure that button ID is unique.
-  // @todo Should this do a case-insensitive comparison?
   $button_id = $form_state->getValue('id');
-  if (in_array($button_id, $button_ids)) {
+  if (in_array($button_id, $button_ids, TRUE)) {
     $form_state->setErrorByName('id', t('A CKEditor button with ID %id already exists.', ['%id' => $button_id]));
   }
 }
@@ -50,8 +54,10 @@ function embed_form_filter_format_add_form_alter(array &$form) {
 
 /**
  * Validate callback for buttons that have a required_filter_plugin_id.
+ *
+ * @todo Remove this once CKEditor4 support is dropped.
  */
-function embed_filter_format_edit_form_validate($form, FormStateInterface $form_state) {
+function embed_filter_format_edit_form_validate($form, FormStateInterface $form_state): void {
   if ($form_state->getTriggeringElement()['#name'] !== 'op') {
     return;
   }
@@ -93,7 +99,7 @@ function embed_filter_format_edit_form_validate($form, FormStateInterface $form_
     };
 
     foreach ($buttons_to_validate as $button_id => $filter_plugin_id) {
-      list($plugin_id, $button_id) = explode(':', $button_id, 2);
+      [$plugin_id, $button_id] = explode(':', $button_id, 2);
       if (in_array($button_id, $selected_buttons, TRUE)) {
         $filter_enabled = $form_state->getValue([
           'filters',
diff --git a/src/Access/EmbedButtonEditorAccessCheck.php b/src/Access/EmbedButtonEditorAccessCheck.php
index 01463b6..fbc8b83 100644
--- a/src/Access/EmbedButtonEditorAccessCheck.php
+++ b/src/Access/EmbedButtonEditorAccessCheck.php
@@ -78,20 +78,29 @@ class EmbedButtonEditorAccessCheck implements AccessInterface {
    *   currently only capable of detecting buttons used by CKEditor.
    */
   protected function checkButtonEditorAccess(EmbedButtonInterface $embed_button, EditorInterface $editor) {
-    if ($editor->getEditor() !== 'ckeditor') {
+    if (!in_array($editor->getEditor(), ['ckeditor', 'ckeditor5'], TRUE)) {
       throw new HttpException(500, 'Currently, only CKEditor is supported.');
     }
 
     $has_button = FALSE;
     $settings = $editor->getSettings();
-    foreach ($settings['toolbar']['rows'] as $row) {
-      foreach ($row as $group) {
-        if (in_array($embed_button->id(), $group['items'])) {
-          $has_button = TRUE;
-          break 2;
+    if ($editor->getEditor() === 'ckeditor') {
+      foreach ($settings['toolbar']['rows'] as $row) {
+        foreach ($row as $group) {
+          if (in_array($embed_button->id(), $group['items'])) {
+            $has_button = TRUE;
+            break 2;
+          }
         }
       }
     }
+    elseif ($editor->getEditor() === 'ckeditor5') {
+      // The schema for CKEditor5 has changed, therefore we need to check for
+      // the toolbar items differently.
+      if ($settings['toolbar']['items'] && in_array($embed_button->id(), $settings['toolbar']['items'])) {
+        $has_button = TRUE;
+      }
+    }
 
     return AccessResult::allowedIf($has_button)
       ->addCacheableDependency($embed_button)
diff --git a/src/Deriver/EmbedCKEditor5PluginDeriver.php b/src/Deriver/EmbedCKEditor5PluginDeriver.php
new file mode 100644
index 0000000..b3f1f11
--- /dev/null
+++ b/src/Deriver/EmbedCKEditor5PluginDeriver.php
@@ -0,0 +1,75 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Drupal\embed\Deriver;
+
+use Drupal\ckeditor5\Plugin\CKEditor5PluginDefinition;
+use Drupal\Component\Plugin\Derivative\DeriverBase;
+use Drupal\Component\Utility\Html;
+use Drupal\Core\Entity\EntityTypeManagerInterface;
+use Drupal\Core\Plugin\Discovery\ContainerDeriverInterface;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+class EmbedCKEditor5PluginDeriver extends DeriverBase implements ContainerDeriverInterface {
+
+  use StringTranslationTrait;
+
+  /**
+   * The entity type manager.
+   *
+   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
+   */
+  protected $entityTypeManager;
+
+  /**
+   * Constructs a new DrupalEntityDeriver object.
+   *
+   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
+   *   The entity type manager.
+   */
+  public function __construct(EntityTypeManagerInterface $entity_type_manager) {
+    $this->entityTypeManager = $entity_type_manager;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, $base_plugin_id) {
+    return new static(
+      $container->get('entity_type.manager')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDerivativeDefinitions($base_plugin_definition) {
+    assert($base_plugin_definition instanceof CKEditor5PluginDefinition);
+
+    /** @var \Drupal\embed\EmbedButtonInterface $embed_button */
+    foreach ($this->entityTypeManager->getStorage('embed_button')->loadByProperties(['type' => $base_plugin_definition->id()]) as $embed_button) {
+      $embed_button_id = $embed_button->id();
+      $embed_button_label = Html::escape($embed_button->label());
+      $plugin_id = "{$base_plugin_definition->id()}_{$embed_button_id}";
+      $definition = $base_plugin_definition->toArray();
+      $definition['id'] .= $embed_button_id;
+      $definition['drupal']['label'] = $this->t('@base - @label', ['@base' => $base_plugin_definition->label(), '@label' => $embed_button_label])->render();
+      $definition['drupal']['toolbar_items'] = [
+        $embed_button_id => [
+          'label' => $embed_button_label,
+        ],
+      ];
+      foreach ($definition['drupal']['elements'] as $element) {
+        if (str_contains('data-embed-button', $element)) {
+          $definition['drupal']['elements'][] = str_replace('data-embed-button', "data-embed-button=\"{$embed_button_id}\"", $element);
+        }
+      }
+      $this->derivatives[$plugin_id] = new CKEditor5PluginDefinition($definition);
+    }
+
+    return $this->derivatives;
+  }
+
+}
\ No newline at end of file
diff --git a/src/Plugin/CKEditor5Plugin/EmbedCKEditor5PluginBase.php b/src/Plugin/CKEditor5Plugin/EmbedCKEditor5PluginBase.php
new file mode 100644
index 0000000..a0da1fd
--- /dev/null
+++ b/src/Plugin/CKEditor5Plugin/EmbedCKEditor5PluginBase.php
@@ -0,0 +1,138 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Drupal\entity_embed\Plugin\CKEditor5Plugin;
+
+use Drupal\ckeditor5\Plugin\CKEditor5PluginDefault;
+use Drupal\ckeditor5\Plugin\CKEditor5PluginDefinition;
+use Drupal\Component\Plugin\Exception\InvalidPluginDefinitionException;
+use Drupal\Component\Utility\Html;
+use Drupal\Core\Access\CsrfTokenGenerator;
+use Drupal\Core\Entity\EntityTypeManagerInterface;
+use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
+use Drupal\embed\Controller\EmbedController;
+use Drupal\embed\EmbedButtonInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Provides a base class for embed CKEditor5 plugins.
+ *
+ * When using your annotation should look something like this:
+ *
+ * @code
+ *   id = "your_embed_type_plugin_id",
+ *   label = @Translation("Your label"),
+ *   ckeditor5 = @CKEditor5AspectsOfCKEditor5Plugin(
+ *     plugins = {"yourModule.YourEmbedTypePluginId"},
+ *     config = {},
+ *   ),
+ *   drupal = @DrupalAspectsOfCKEditor5Plugin(
+ *     deriver = "Drupal\embed\Deriver\EmbedCKEditor5PluginDeriver",
+ *     elements = {
+ *       "<your-embed-tag>",
+ *       "<your-embed-tag data-embed-button>",
+ *     },
+ *     conditions = {
+ *       "filter" = "your_embed_filter_id",
+ *     },
+ *   ),
+ * @endcode
+ *
+ * @see \Drupal\ckeditor5\Annotation\CKEditor5Plugin
+ */
+abstract class EmbedCKEditor5PluginBase extends CKEditor5PluginDefault implements ContainerFactoryPluginInterface {
+
+  /**
+   * The CSRF Token generator.
+   *
+   * @var \Drupal\Core\Access\CsrfTokenGenerator
+   */
+  protected $csrfTokenGenerator;
+
+  /**
+   * The entity type manager.
+   *
+   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
+   */
+  protected $entityTypeManager;
+
+  /**
+   * DrupalEntity constructor.
+   *
+   * @param array $configuration
+   *   A configuration array containing information about the plugin instance.
+   * @param string $plugin_id
+   *   The plugin_id for the plugin instance.
+   * @param \Drupal\ckeditor5\Plugin\CKEditor5PluginDefinition $plugin_definition
+   *   The plugin implementation definition.
+   * @param \Drupal\Core\Access\CsrfTokenGenerator $csrf_token_generator
+   *   The CSRF Token generator service.
+   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
+   *   The Entity Type Manager service.
+   */
+  public function __construct(array $configuration, string $plugin_id, CKEditor5PluginDefinition $plugin_definition, CsrfTokenGenerator $csrf_token_generator, EntityTypeManagerInterface $entity_type_manager) {
+    parent::__construct($configuration, $plugin_id, $plugin_definition);
+    $this->csrfTokenGenerator = $csrf_token_generator;
+    $this->entityTypeManager = $entity_type_manager;
+    if (!isset($plugin_definition['embed_type_id'])) {
+      throw new InvalidPluginDefinitionException($plugin_id, sprintf('The %s plugin must define the embed_type_id property.', $plugin_id));
+    }
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
+    return new static(
+      $configuration,
+      $plugin_id,
+      $plugin_definition,
+      $container->get('csrf_token'),
+      $container->get('entity_type.manager')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getButtons(): array {
+    $buttons = [];
+
+    if ($embed_buttons = $this->entityTypeManager->getStorage('embed_button')->loadByProperties(['type_id' => $this->pluginDefinition['embed_type_id']])) {
+      foreach ($embed_buttons as $embed_button) {
+        $buttons[$embed_button->id()] = $this->getButton($embed_button);
+      }
+    }
+
+    return $buttons;
+  }
+
+  /**
+   * Build the information about the specific button.
+   *
+   * @param \Drupal\embed\EmbedButtonInterface $embed_button
+   *   The embed button.
+   *
+   * @return array
+   *   The array for use with getButtons().
+   */
+  protected function getButton(EmbedButtonInterface $embed_button): array {
+    $label = Html::escape($embed_button->label());
+
+    return [
+      'id' => $embed_button->id(),
+      'name' => $label,
+      'label' => $label,
+      'image' => $embed_button->getIconUrl(),
+    ];
+  }
+
+  /**
+   * Get the embed preview route CSRF token.
+   */
+  public function getEmbedPreviewCsrfToken(): string {
+    return $this->csrfTokenGenerator->get(EmbedController::PREVIEW_CSRF_TOKEN_NAME);
+  }
+
+}
\ No newline at end of file
diff --git a/tests/src/Functional/EmbedButtonEditorAccessCheckTest.php b/tests/src/Functional/EmbedButtonEditorAccessCheckTest.php
index e8cdf78..2df5d86 100644
--- a/tests/src/Functional/EmbedButtonEditorAccessCheckTest.php
+++ b/tests/src/Functional/EmbedButtonEditorAccessCheckTest.php
@@ -2,29 +2,85 @@
 
 namespace Drupal\Tests\embed\Functional;
 
+use Drupal\editor\EditorInterface;
 use Drupal\editor\Entity\Editor;
+use Drupal\embed\Access\EmbedButtonEditorAccessCheck;
 use Drupal\Tests\system\Functional\Cache\AssertPageCacheContextsAndTagsTrait;
 
 /**
  * Tests EmbedButtonEditorAccessCheck.
  *
+ * @coversDefaultClass \Drupal\embed\Access\EmbedButtonEditorAccessCheck
  * @group embed
  */
 class EmbedButtonEditorAccessCheckTest extends EmbedTestBase {
 
   use AssertPageCacheContextsAndTagsTrait;
 
-  const SUCCESS = 'Success!';
-
   /**
    * {@inheritdoc}
    */
-  protected $defaultTheme = 'stark';
+  protected static $modules = [
+    'ckeditor',
+    'ckeditor5',
+  ];
+
+  /**
+   * Sets up the editor for testing.
+   *
+   * @param string $editor_id
+   *   The editor plugin ID.
+   *
+   * @return \Drupal\editor\EditorInterface
+   *   The saved editor entity.
+   */
+  public function setupEditor(string $editor_id): EditorInterface {
+    $editor = Editor::create([
+      'format' => 'embed_test',
+      'editor' => $editor_id,
+    ]);
+
+    switch ($editor_id) {
+      case 'ckeditor':
+        $editor->setSettings([
+          'toolbar' => [
+            'rows' => [[[
+              'name' => 'Embed',
+              'items' => [
+                'embed_test_default',
+              ],
+            ]]],
+          ],
+        ]);
+        break;
+
+      case 'ckeditor5':
+        $editor->setSettings([
+          'toolbar' => [
+            'items' => [
+              'embed_test_default',
+            ],
+          ],
+        ]);
+        break;
+
+      default:
+        $this->fail("Unsupported editor plugin $editor_id.");
+    }
+
+    $editor->save();
+    return $editor;
+  }
 
   /**
    * Tests \Drupal\embed\Access\EmbedButtonEditorAccessCheck.
+   *
+   * @covers ::access
+   * @dataProvider providerEmbedbuttonEditorAccessCheck
    */
-  public function testEmbedButtonEditorAccessCheck() {
+  public function testEmbedButtonEditorAccessCheck(string $editor) {
+    $this->setUpEditor($editor);
+
     // The anonymous user should have access to the plain_text format, but it
     // hasn't been configured to use an editor yet.
     $this->getRoute('plain_text', 'embed_test_default');
@@ -52,7 +108,7 @@ class EmbedButtonEditorAccessCheckTest extends EmbedTestBase {
     // Add an empty configuration for the plain_text editor configuration.
     $editor = Editor::create([
       'format' => 'plain_text',
-      'editor' => 'ckeditor',
+      'editor' => $editor,
     ]);
     $editor->save();
     $this->getRoute('plain_text', 'embed_test_default');
@@ -66,7 +122,7 @@ class EmbedButtonEditorAccessCheckTest extends EmbedTestBase {
     $this->assertCacheContext('route');
     $this->assertSession()->responseHeaderContains('X-Drupal-Cache-Tags', 'config:editor.editor.embed_test');
     $this->assertSession()->responseHeaderContains('X-Drupal-Cache-Tags', 'config:embed.button.embed_test_default');
-    $this->assertSession()->pageTextContains(static::SUCCESS);
+    $this->assertSession()->pageTextContains('Success!');
 
     // Test route with an empty request.
     $this->getRoute('embed_test', 'embed_test_default', '');
@@ -90,6 +146,15 @@ class EmbedButtonEditorAccessCheckTest extends EmbedTestBase {
     $this->assertSession()->responseHeaderNotContains('X-Drupal-Cache-Tags', 'config:embed.button.invalid_button');
   }
 
+  /**
+   * Data provider for testEmbedbuttonEditorAccessCheck().
+   */
+  public function providerEmbedbuttonEditorAccessCheck(): array {
+    return array_map(static function (string $editor_id) {
+      return [$editor_id];
+    }, ['ckeditor', 'ckeditor5']);
+  }
+
   /**
    * Performs a request to the embed_test.test_access route.
    *
@@ -106,7 +171,7 @@ class EmbedButtonEditorAccessCheckTest extends EmbedTestBase {
   public function getRoute($editor_id, $embed_button_id, $value = NULL) {
     $url = 'embed-test/access/' . $editor_id . '/' . $embed_button_id;
     if (!isset($value)) {
-      $value = static::SUCCESS;
+      $value = 'Success!';
     }
     return $this->drupalGet($url, ['query' => ['value' => $value]]);
   }
diff --git a/tests/src/Functional/EmbedTestBase.php b/tests/src/Functional/EmbedTestBase.php
index bc86f60..16a921e 100644
--- a/tests/src/Functional/EmbedTestBase.php
+++ b/tests/src/Functional/EmbedTestBase.php
@@ -25,7 +25,6 @@ abstract class EmbedTestBase extends BrowserTestBase {
     'embed',
     'embed_test',
     'editor',
-    'ckeditor',
   ];
 
   /**
@@ -61,23 +60,6 @@ abstract class EmbedTestBase extends BrowserTestBase {
     ]);
     $format->save();
 
-    $editor_group = [
-      'name' => 'Embed',
-      'items' => [
-        'embed_test_default',
-      ],
-    ];
-    $editor = Editor::create([
-      'format' => 'embed_test',
-      'editor' => 'ckeditor',
-      'settings' => [
-        'toolbar' => [
-          'rows' => [[$editor_group]],
-        ],
-      ],
-    ]);
-    $editor->save();
-
     // Create a user with required permissions.
     $this->adminUser = $this->drupalCreateUser([
       'administer embed buttons',
diff --git a/tests/src/FunctionalJavascript/EmbedButtonAdminTest.php b/tests/src/FunctionalJavascript/EmbedButtonAdminTest.php
index c4c9490..ee279c4 100644
--- a/tests/src/FunctionalJavascript/EmbedButtonAdminTest.php
+++ b/tests/src/FunctionalJavascript/EmbedButtonAdminTest.php
@@ -188,12 +188,13 @@ class EmbedButtonAdminTest extends WebDriverTestBase {
 
     $id = $assert_session->waitForField('id');
     $this->assertNotEmpty($id);
-    $id->setValue('DrupalImage');
+    $id->setValue('drupalimage');
 
     $edit = [
       'type_id' => 'embed_test_default',
     ];
     $this->submitForm($edit, 'Save');
+    $assert_session->pageTextContains('A CKEditor button with ID DrupalImage already exists.');
   }
 
 }